High blood pressure: How low should you go?

People with hypertension are generally advised to lower their blood pressure to reduce their risk of having a heart attack or a stroke, but how low should they aim for? New research suggests it might not be necessary to lower the blood pressure all the way to normal levels to reduce the risk of serious problems.

Hypertension, or high blood pressure, is diagnosed in people who have a systolic blood pressure(the "top" blood pressure number) above 140 mm Hg. Patients with hypertension are often treated to reduce their blood pressure to normal levels, of 120 mm Hg or less.

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"Frequently, we treat patients' blood pressure to the lowest it will go, thinking that is what's best," study researcher Dr. Carlos Rodriguez, associate professor of public health sciences at Wake Forest Baptist, said in a statement.

In the new study, Rodriguez and colleagues looked at nearly 4,500 people and followed them for 21 years, measuring their systolic blood pressure every three years. Participants' systolic blood pressure ranged from less than 120 to greater than 140.

By the end of the study period, there were 1,622 cases of heart problems, including heart failure, heart attack and stroke. People with high blood pressure (above 140) had a 46 percent higher risk of developing heart problems compared with people who had blood pressurebelow 120.

But the researchers also found there was no difference in heart disease risk between people with a systolic blood pressure in the 120-to-139 range, and people with blood pressure below 120, according to the study published today (June 16) in the journal JAMA Internal Medicine. [7 Ways to Lower Your Risk of Heart Disease]

The findings suggest that once systolic blood pressure is brought below 140, lowering it further, to less than 120 may not provide additional heart health benefit for patients, according to the study.

"This calls into question the notion that lower is better," Rodriguez said.

In the study, the researchers controlled for other factors that can affect heart health, such as age, gender, body mass index, cholesterol levels, smoking habits and alcohol consumption.

The findings were similar among men, women and different races. However, the researchers found that African-Americans, who have a higher risk of hypertension than Caucasians, were more likely to have a reduced risk of heart disease risk from lowering their blood pressure to below 140, compared with any other group.

For most patients with hypertension, a treatment goal of 120 to 139 mm Hg may be acceptable, and it will significantly reduce the risk of stroke, heart attack or heart failure, the researchers said. However, these results need to be confirmed in future studies, they added.

About 1 in 3 adults in the United States or 67 million people have high blood pressure, and only about half of them have their condition under control, according to the Centers for Disease Control and Prevention (CDC).

Hypertension often has no warning signs or symptoms, and is detected by measuring blood pressure. The condition is linked to a variety of health problems, most notably heart conditions.

Eating a healthy diet, quitting smoking and exercising are important lifestyle factors to prevent hypertension, according to the CDC.

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